Method of recovering gold



United States Patent METHOD OF RECOVERING GOLD Fred E. Kentz, Denver, C010.

No Drawing. Application December 3, 1951, Serial No. 259,727

6 Claims. (Cl. 209-49) This invention relates tothe separation and recovery of gold and has as an object to provide a novel and effective method for the extraction of native gold from the sands and gangue with which it is naturally associated.

A further object of the invention is to provide an 1mproved method for the recovery of native gold that 1s simple and convenient of field practice through the use of readily-available agents and facilities.

A further object of the invention is to provlde an improved method for the recovery of native gold that 1s distinguished by remarkably high eificrency 1n the capture of minute value particles.

A further object of the invention is to provide an 1mproved method for the recovery of native gold that particularly effective in separating value particles from black sands and analogous magnetite gangue.

A further object of the invention is to provide an improved method for the recovery of native gold that applies hitherto unrecognized properties of a known material to extend the practicality and efiiciency of conventionally-established techniques.

With the foregoing and other objects in view, my invention consists in the nature, correlation, and peculiarity of sequential steps, and in the method thereby constituted, all as hereinafter set forth and pointed out in my claims.

As is well known, gold in its native, or free, state is widely distributed intermixed and variously associated with sands, rocks, sediments, and the like, wherein the values may occur in the form of grains and flakes, sometimes so fine as to be practically invisible, wires, seams, and nuggets. Whatever may be its natural occurrence, whether in placer sands or rock ores, the gold is readily conditioned for separation from the associated gangue or matrix, a simple size-grading, or screening, being adequate to so condition the gold-bearing sands and conventional crushing, grinding, and screening serving to similarly condition the gold-bearing ores. Thus, irrespective of initial character, the gold-bearing material to be treated for recovery of values is presented to the separating and recovering operation in the form of a screened, or size-graded, admixture of value particles and sand or gangue grains capable of mixing with water in and as a freely-flowing pulp, and the techniques of the improved method hereinafter described are applied lto and for the treatment of gold-bearing material conditioned as above set forth, without regard to the initial character and occurrence of the material or any conditioning treatment thereof.

While the freely-separable nature and high specific gravity of native gold contribute to facility of its isolation and recovery from the associated sands and gangue, the frequently very minute size of the value particles and the sometimes high specific gravity of the associated matter, particularly characteristic of black sands and magnetite, seriously complicate the simpler recovery techniques and often determine the practicality and economic feasibility of Working a given deposit. Historically and conventionally, preferred methods for separating native gold from the associated gangue have relied upon the specific gravity differential to settle out the value particles from a thin pulp of the gold-bearing material caused to flow through sluices, over vibrating tables or jigs, through and across particularly constructed pans, and the like, and have utilized riffies, fleeces, blankets, and like eddydeveloping instrumentalities, with or without the supplementary amalgamating functions of mercury, to en- 2,706,553 Patented Apr. 19, 1955 trap and hold the so-separated values. Such preferred separatory methods have advantages of convenience, facility, and economy offset, in a great many instances, by excessive loss of the very minute value particles and by very low efiiciency in the treatment of materials containing black sands and magnetite, hence the instant invention is directed to a novel extension and inexpensive modification of the simple separatory methods heretofore used whereby the separatory efficiency thereof is enhanced for successful adaptation of such methods to recoveries from black sands and magnetite materials and to the recovery of values hitherto lost.

The novelty and efficiency of the improved method derive from recognition of certain properties characterizing a range of residual oil cuts or fractions obtained through the distillation of petroleum after the volatiles have been drawn off and subsequent to the removal of the lubricating oils, such residual oil products being wellknown and widely marketed for particular lubricating purposes under various specific names and designations and in accordance with establisheddistinguishing specifications. It has been known that some of the residual oil cuts or fractions have a marked afiinity for metal to which they tenaciously adhere in a manner and to a degree well qualifying them for lubricants on gears, chains, and analogous elements, and for the coating of metal surfaces, but it does not appear to have been previously known that such afiinities of the residual oil products were susceptible of simple manipulation as to their selectivity for particular metals whereby to condition the product for adherence to one, and not to another, of two or more metals to which it is exposed. Commercially-available residual oil cuts and fractions having the properties and characteristics conditioning them for desired functioning in the improved gold-recovery method are classed for marketing purposes as chain lubricants and gear lubricants and comprise an extensive category within the frame of established specifications whereby the identity and peculiar properties of a particular such product may be fixed. Typical of such products, and of their identifying specifications, a residual oil fraction successfully utilized in the practice of the improved method is marketed by the Texas Oil Company as a Chain Lubricant under the designation Crater No. 3. This product is found on analysis to be a residual oil of asphaltic origin from which both gasoline and lubricating oil fractions have been removed by straight distillation and it has added thereto no extraneous additives, and has the following specific characteristics:

metals characterizing residual oil products of the type above set forth is pronounced with respect to native gold and is of a degree to grip and hold particles of gold in a stream of Water washed over an exposed surface area of the residual oil material, and it has also been determined that the adherent afiinity of the residual oil material for metals other than gold is minimized by flow of water over the material surface to such extent as to wash any particles of the other metals, or non-metallic particles, entrained by the flow across the surface Without entrapment of the non-gold particles thereon, thus establishing a selective adherent afiinity for the gold which may be applied to separation of the values from the associated gangue, even when the latter is of metallic character and of a high specific gravity.

Utilizing the properties of the typical residual oil fractions above elaborated, the improved method is susceptible of simple and convenient practice to separate and recover a very high proportion of the gold values associated with sands and granular gangues of all types. In one practical application of the method, a sluice or launder of any appropriate material and construction is longitudinally inclined for gravity-induced flow of water therethrough and a section of the sluice or launder floor exposed to such flow is evenly and thinly coated with a dressing of the typical residual oil fraction, such as Crater No. 3 or the equivalent. The dressing may be applied directly upon and will adhere to the floor area of the sluice or launder when the latter is dry and of appropriate material, such as metal, or, as will be obvious, the dressing may be spread to cover one surface of a thin plate adapted for removable and replaceable association with and as an area of the sluice floor. A desired and appropriately extensive area of the sluice floor having been dressed with the residual oil fraction coating, the surface of such dressing is thoroughly wetted, as by flowing water thereover through the sluice and frictionally spreading the water into intimate engagement with all areas of said surface, and the gold-bearing material to be treated is fed, in any appropriate manner and through any suitable agency, as a thin pulp to and for flow through the sluice across the dressed floor area thereof. As should be manifest, a flow of water may be established in and maintained through the sluice and the conditioned goldbearing material may be fed dry thereto through an ore feeder at the sluice upper end, or, alternatively, the gold-bearing material may be mixed with water to form a thin pulp prior to feed of the mixture to the sluice, both of such techniques being conventional in analogous operations. As the thin pulp of gold-bearing material flows along the sluice the gold particles settle toward the sluice floor, as is well understood, so that the values come into close contact with the dressed surface area of the sluice floor as the flow traverses the latter and the adherent affinity of the dressing material then operates to grip and hold the value particles while permitting the flow to carry all other constituents of the ore material, including the black sands and magnetite particles, across and past the dressed floor area without hesitation. When it becomes manifest that the dressed area has become so loaded with value particles as to lose its effectiveness for such purpose, the flow across the area is interrupted, the gold-charged dressing is removed, a new dressing, or dressed area is provided, and the flow is reestablished for continuation of the separatory operation.

The nature of the dressing and gold-entrapping material is such as to very much facilitate its removal from the area on which it has been spread and to expedite recovery of the entrapped gold therefrom. The dressing and entrapping material being a petroleum residual oil, it is soluble in the petroleum volatiles, such as naptha, benzene, gasoline, kerosene, and the like, as well as in other, perhaps more expensive vehicles, hence it is readily washed, with its value content, from the area over which it was spread through the agency of a suitable solvent and enters into solution therewith to release the gold particles from which the solution may be easily decanted, filtered, evaporated, or otherwise removed, thus completing the desired recovery.

When deemed to be expedient, the sluice floor may be equipped with riflles, pockets, and analogous flow-modifying features interrupting the dressed area to function in their well-known and expected manner for facilitation of the separatory stage as above described. Similarly, the flow of gold-bearing pulp may be directed across vibrating tables, pans, and jigs of known construction and operative effect whereof areas underlying and in contact with the pulp flow have been dressed as above set forth, all to more effectively utilize the peculiar adherent aflinity of the dressing material and to realize the manifest advantages thereof, as described in relation to the simple sluice technique above elaborated.

Since particular adaptations and detail variations within the spirit of the invention are many, I wish to be understood as being limited solely by the scope of the appended claims, rather than by any exemplary details of the foregoing description.

I claim as my invention:

1. The method of recovering native gold from sands and comminuted ores which consists of coating the surface of an area with a residual petroleum fraction of asphaltic origin having a Saybolt-Furol viscosity of 210 F. of about 300 seconds and having a high adherent affinity for metals, intimately water-wetting the exposed surface of said coating, flowing the gold-bearing material as a thin water pulp in direct engagement with and across the wetted coating surface, whereby to entrap the value particles in and on the coating, subsequently washing the value-charged coating from the area with a suitable solvent, and separating the values from the solution of coating and solvent.

2. The method of recovering native gold from sands and comminuted ores characterized by flowing a thin water pulp of the gold-bearing material in direct engagement with and across the precedently-wetted surface of an area coated with a residual petroleum fraction of asphaltic origin having a Saybolt-Furol viscosity of 210 F. of about 300 seconds.

3. The method of recovering native gold from sands and comminuted ores distinguished by exposure of a thin water pulp of the gold-bearing material to the precedentlywetted surface of a residual petroleum fraction of asphaltic origin having a Saybolt-Furol viscosity at 210 F. of about 300 seconds having a high adherent aflinity for metals for the segregation of value particles from the pulp.

4. In a gold-recovery method characterized by flow of gold-bearing sands and comminuted ores in the form of a thin water pulp, a trap for the segregation of value particles from said pulp, said trap comprising a flowexposed area coated with a residual petroleum fraction of asphaltic origin having a Saybolt-Furol viscosity at 210 F. of about 300 seconds.

5. In a gold-recovery method characterized by flow of gold-bearing sands and comminuted ores in the form of a thin water pulp, a trap for the segregation of value particles from said pulp, said trap comprising a flowexposed area coated with a residual petroleum fraction of asphaltic origin oil from which volatile gasoline and lubricating oils have been removed by distillation having a gravity of 10.7, a flash point of 515, a fire point of 600, pourable at F., a Saybolt viscosity of 300 at 210 F., a sulfur content of 2.34%, and a negative corrosion factor and conditioned by advance water-wetting of its exposed surface.

6. In a gold-recovery method characterized by flow of gold-bearing sands and comminuted ores in the form of a thin water pulp, a trap for the segregation of value particles from said pulp, said trap comprising a flowexposed area coated with a residual petroleum fraction of the type marketed as a chain-lubricant under the designation Crater No. 3 and conditioned by advance waterwetting of its exposed surface said oil being a residual asphaltic origin oil having a gravity of 10.7, a flash point 515, a fire point of 600, pourable at plus 85 degrees F., a Saybolt viscosity of 300 at 210 degrees F., a sulphur content of 2.34 per cent and a negative corrosion.

References Cited in the file of this patent UNITED STATES PATENTS 899,149 Wolf Sept. 22, 1908 1,607,845 Parker Nov. 23, 1926 1,970,701 Kratz Aug. 21, 1934 2,101,572 Broatch Dec. 7, 1937 2,183,971 Miller Dec. 19, 1939 OTHER REFERENCES Thomsen: The Practice of Lubrication, 1951, pp. 30, 31, 32, 138, 575, 576. Copy in Div. 64. 

1. THE METHOD OF RECOVERING NATIVE GOLD FROM SANDS AND COMMINUTED ORES WHICH CONSISTS OF COATING THE SURFACE OF AN AREA WITH A RESIDUAL PETROLEUM FRACTION OF ASPHALTIC ORIGIN HAVING A SAYBOLT-FUROL VISCOSITY OF 210* F. OF ABOUT 300 SECONDS AND HAVING A HIGH ADHERENT AFFINITY FOR METALS, INTIMATELY WATER-WETTING THE EXPOSED SURFACE OF SAID COATING, FLOWING THE GOLD-BEARING MATERIAL AS A THIN WEATER PULP IN DIRECT ENGAGEMENT WITH AND ACROSS THE WETTED COATING SURFACE, WHEREBY TO ENTRAP THE VALUE PARTICLES IN AND ON THE COATING, SUBSEQUENTLY WASHING THE VALUE-CHARGED COATING FROM THE AREA WITH A SUITABLE SOLVENT, AND SEPARATING THE VALUES FROM THE SOLUTION OF COATING AND SOLVENT. 